280 PROCEEDINGS OF THE INDIANA ACADEMY OF SCIENCE. 



boiler, covered with distilled water and the double boiler placed over a 

 bunsen burner. 



Handling of Soil Sample 



When the samples reached the laboratory thej^ are set out in a row on tlie 

 laboratory table where the apparatus has already been arranged. The 

 bunsen burner is lighted and the saucepan and aluminum spoon are sterilized 

 by passing them through the free flame several times. The pan is set down 

 on the bench and the spoon placed inside of it. A sampler containing a sampie 

 of soil is wiped off with a towel to free it from loose soil on the outisde, the 

 light mallet is sterilized in the free flame and placed in the sterile saucepan. 

 The outside of the sampler is sterilized in the flame. The cap is removed from 

 the sampler, and laid to one side The sampler is held, witli the left hand, 

 over the saucepan and struck with the mailet, the soil falls out into the pan. 

 (We have found this the most efficient way of removing the soil from the 

 sampler unless the soil is frozen.) The soil is now thoroughly mixed with the 

 aluminum spoon. 



Place one of the nreviously weighed t.»elve ounce bottle? on one pan of 

 the balance and then place 50 grams more than the bottle weighs on the 

 other pan. Remove the cotton plug flame the mouth of the liottle, place the 

 bottle on the balance pan and lay the cotton plug top down in the balance 

 pan beside the bottle. By means of the aluminum spoon quickly introduce 

 fifty grams of soil into the l)ottle, flame, then replace the cotfon plug and set 

 the bottle to one side. 



Into each of three of the jell glasses weigh out one hundred grams of the 

 soil, for conducting the physiological tests, and set the jell glasses to one side. 

 Weigh out on a paper 50 gms. of the soil and put it in one of the 16 ounce 

 saltmouth bottles. (This is the aliquot for the determination of nitrates 

 present in the field soil.) Put the remainder of the sample in one of the Mason 

 jars and seal the jar. Clean (he graniteware pan and aluminum spoon. 

 Usually all the visable soil is removed by wiping with a piece of absorbent 

 cotton. Each of the other samples of soil is handled in the same way. The 

 heat is started under the double boiler containing the rubber stoppers and 

 preparations are made to melt the media and get it in the 40°C water bath. 

 If proper preparations were made the media can be melted and prepared 

 while the dilutions are being made. 



Making Bacterial Dilutions 



The sterile graduated cylinders and the tank of sterile water are placed 

 on the laboratory talkie and sterile water drawn off as follows. Remove the 

 test tul)e of alcohol that is over the outlet to the tank, allow about a i)int of 

 water to run out and discard it. Flame the cotton plug of the 200 cc. graduated 

 cylinder, removi" it. flame the mouth of the cylinder, and then by means of 

 the graduated cylinder add 200 cc. of the sterile water to each of the 10 twelve 



